Impact of nuclear masses on r-process nucleosynthesis: bulk properties versus shell effects

TL;DR

This study shows that r-process nucleosynthesis is mainly affected by local shell effects in nuclear masses rather than bulk properties, guiding future research focus.

Contribution

It decomposes nuclear mass models into bulk and shell components, highlighting the importance of local shell effects on abundance variations.

Findings

Abundance distribution is insensitive to bulk mass variations.

Local shell effects significantly influence r-process abundance patterns.

Focus on local mass changes is crucial for understanding nucleosynthesis.

Abstract

We investigate the impact of the model estimating the masses of exotic nuclei on r-process nucleosynthesis, assessing the dependence of the abundance distribution on the specific properties of nuclear masses. By decomposing theoretical nuclear mass predictions into a liquid-drop parametrization and local shell effects, we show that r-process abundances are virtually insensitive to large variations of the masses which originate from nuclear bulk properties of the model, such as the symmetry energy. In contrast, the mass component associated with local shell effects is the main driver of r-process abundance variations, despite its relatively minor contribution to the absolute value of neutron separation energies. Our work suggests that experimental and theoretical studies of masses devoted to r-process applications, such as the nucleosynthesis in the ejecta of neutron star mergers, should focus on the physical origin and determination of local changes in mass trends.